Direct Simulation VS Inverse Simulation
Before finding an Integration Angle for your system, this page provides you with comparisons of direct simulations with an Integration Angle VS inverse simulations.
This will show you the main differences, but keep in mind that there is no right or wrong answer. The examples consider that an adequate integration angle is set.
Example: Direct Simulation with Integration Angle VS Inverse Simulation
The following example represents an automotive light guide. Two simulations have be carried out, one direct simulation and one inverse simulation.
In this case, you can see that the Direct Simulation is more efficient compared to the Inverse Simulation for an equal simulation time.
_Integration_Angle_Light_Guide_Example.png)
| Direct Simulation | Inverse Simulation |
|---|---|
Simulation time = 25 minutes Integration angle = 5° |
Simulation time = 25 minutes |
_Integration_Angle_Light_Guide_Direct_Result.png) |
_Integration_Angle_Light_Guide_Inverse_Result.png) |
Example: Integration Angle Effect on Result
Three examples are provided to illustrate the integration angle effect on a Radiance map (image of a phone seen through a window (specular surface)).
Each result is obtained with an equal number of rays launched into the simulation.
Simulation time = 30 minutes Integration Angle = 10° |
Simulation time = 30 minutes Integration Angle = 1° |
Simulation time = 30 minutes Integration Angle = 3° |
_Sensor_Integration_Angle_Phone_Blurry.png) |
_Sensor_Integration_Angle_Phone_Noisy.png) |
_Sensor_Integration_Angle_Phone_Adequate.png) |
Blurry A blurry result means the integration angle is too big. Too many rays are integrated by the sensor. |
Noisy A noisy result means the integration angle is too small. Not enough rays are integrated by the sensor. |
Adequate A balanced result is obtained when the integration angle is well adjusted to the scene. |
Advantages and Drawbacks
Direct Simulation Advantages
- The bigger your system is (adding diffusing material, hidden sources, etc.), the more the direct simulation outperforms the inverse simulation.
- The more the sources are hidden behind optics, the longer the light path is from the source to the sensor, the better the direct simulation compared to the inverse simulation.
- The direct simulation is usually faster than the inverse simulation when there are diffuse materials.
- The direct simulation is usually better when trying to simulate light guides.
Direct Simulation Drawbacks
The Integration Angle is and will always be an approximation. If you set a correct Integration Angle you will narrow down the approximation, but you will not completely remove it.
Inverse Simulation Advantages
- The inverse simulation does not need an Integration Angle. So, the simulation result will be correct without any approximation.
- The inverse simulation is usually better when trying to simulate ambient sources.
Inverse Simulation Drawbacks
The Inverse Simulation is slow and requires more resources (HPC, Cores, etc.) than a Direct Simulation.